I'm working on the design for my rear shock mounts. Anyone have any idea how much uptravel can I realistically expect from the rear end before a 37" tire is touching the inside of the fender on a 3.5" lift with a full width 9"? I'm thinking 6" if the other side is drooped 6"?

It depends on your suspension setup and body clearance....
That said, with my BC rear 3.5" leafs, I was maxing out at around 8.75" of total vertical travel at axle center - when articulated, it was a good bit more at the wheels. My bump stops are roughly 3" above my axles at stock locations but I can still put my tires into the flare at full stuff. That's with gorrilla flares mounted at the body line and 2“ body lift. I don't have full width or spacers though... I do have a decent amount of gear in the Bronco though, so I sit at the height closer to what most would with a 2.5" lift. This means I have more downtravel than up travel as well.

Thanks, that helps. I think that if I put my rear shocks at 6" up travel and the rest down I should have more than enough if I link it. Just didn't want to waste the uptravel. I'm willing to cut as much sheet metal as it takes to make things fit.

6" uptravel should be fine.

Statically with full widths, 3.5" suspension lift and 2" body lift, I have 9" of clearance between the top of the tire and the fender flare. I only have 6" uptravel in front and 5.25" rear, which is not a problem since the rear is more stiffly sprung.

Dont have measurments but it does travel a lot.